Curing laminated sheeting



Patented Apr. 21, 1936 -Y Y- 2,037,744

UNITED STATES PATENT OFFICE CURING LAMINATED SHEETNG Henry E. Van Derhoef, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York Application May 5, 1933, Serial No. 669,530

10 Claims. (Cl. 18-51) This invention relates to the lamination and I have now discovered that the solvent may curing of cellulose derivative sheetingand more be substantially completely removed from the particularly to the lamination of cellulose derivalaminated stock in a relatively short time by tive sheeting by the use of a solvent and the passing it through a water bath, or as it is somecuring of that sheeting by passing it through times termed,.throughawaterboX-such water ,5

water for the removal of that solvent-the latter treatment being termed Water-boxing. being an operation which I term Water-boxing. It is an object of my invention, therefore, to In my Patent No. 1,540,822, I have described -produce laminated cellulose derivative sheeting a method and apparatus for laminating cellulose and more particularly to produce a substantially derivative sheetingso as to form a sheet which non-shrinking laminated stock. Ayiurther object 10 to all intents and purposes is a single, ho'mogeof my invention is to provide a process for lamineous sheet having a thickness approximately nating cellulosederivative sheeting and for curequal to that of the combined thicknesses of the ing the laminated stock by passing it through sheets used for producing the laminated stock. a water bath. Another object of my invention nomical to produce it by first casting thin sheetpletely removing the solvent from laminated ing at a high speed and then laminating that stock. Other objects will be apparent upon furthin sheeting into thicker stock than itis to ther perusal of this specification.

cast thick sheeting at a much slower speed. The In its broader aspects, my invention consists solvent or cementfor effecting adherence of the in laminating two or more strips of relatively 20 sheets together is applied to the sheet in a manthin, cellulose derivative sheeting to form a relaner, such for instance, as that described in my tively thick, laminated sheet, which laminated Patent No. 1,641,403. stock is then treated with a water bath at a While I have successfully employed the above suitable temperature.

$ patented method of producing laminated sheet- The separate sheetings Which are used to build ,25

ing, the process has been found to have the drawup the laminated stock, may be Whatever type back of requiring long curing of the laminated of cellulose derivative desired, such for instance stock, so that the process was found to be one as cellulose nitrate, cellulose acetate, cellulose relatively expensive to operate. 'I'his is true acetate propionate, or the like. These thin sheets Whether the thin .sheeting still contains considmay range from .001 120.006 of an inch in thick- 30 erable solvent or is substantially completely airness approximately, and there may be laminated cured. Furthermore, it became vapparent that two or more sheets, as shown in my Patent No. the complete removal of the solvent from the 1,540,822. These .sheets may be led to the lamilaminated stock was diicult, the reason for this nating device direct from the coating Wheel upon '35 being that the solvent cement is occluded bewhich they are produced, such as described in ,35

tween two substantially cured and relatively hard my aforementioned patent, Yor they may be supsheets, so that the solvent cannot completely plied to the laminating device from stock rolls permeate or travel to the surface of the lamiof sheeting, which have been previously produced nated sheeting and thereby be removed from the Yand stored until ready for laminating. Such -40 stock by mere evaporation. Hence, when the sheeting may be any desired Width, such as forty 40 laminated sheeting was coated with a phototo fifty inches wide as normally produced` on a graphic emulsion t0 produce photographic nlm, casting wheel. Any 1engtn convenient may be and this lm was exposed and subjected to the employed.

11511211 DTOCBSSng, a considerable shrinkage took In the attached diagrammatic elevational drawplace in the lm by virtue of further removal ing, I have illustrated a form of device which .45 of residual solvent from the laminated base by may be used to carry out my invention. In this, the processing solutions. While this is not aparthe supply rolls l and 2 generically represent Vticular fault with some kinds of film, it is with thin sheeting in the form of rolls of thin stock others. For instance, photographic film used for or in the form of sheeting coming from the castv mapping purposes must give va substantially true ing wheel after suitable intervening curing. 50

reproduction to scale of the image and, for that These thin sheets then pass upwardly between purpose for instance, it becomes highly desirable the pressure rolls 3 and 4, a supply of solvent vto have a film which is substantially vnon-shrinkcement being provided by the hopper 5, such as ing upon the processing thereof in the usual phodescribed in my Patent No. 1,641,403. A suitable v5.5 tographic baths. solvent cement for substantially all types of cel- Where thick sheeting is desired, it is more ecois to provide a process for substantially com- 15 I lulose derivative is acetone. This acetone is forced upwardly so as to contact with the thin sheets just prior to the passage of the thin sheeting through the pressure rolls 3 and 4. The acetone acts quite rapidly upon the inner surface of the thin sheeting, reducing those surfaces to a plastic state so that, as the thin sheets pass between the pressure rolls 3 and 4, the surfaces of the thin sheeting unite forming a homogeneous, thick sheeting.

It will be noted, however, that at this stage the sheeting has trapped, in the center lamina thereof, the solvent cement which has been deposited by hopper 5. The laminated stock is then led upward through a casing 6 over rolls 1 and then over heated curing drums 8, these rolls I and dru-ms 8 being enclosed in the casing 6 through which there is circulated warm or hot air to remove from the sheet whatever solvent is available for such removal.

From the last drum 8 the laminated stock is led from the casing 6 over rolls 9 into the waterbox II. In this water-box, the laminated stock is conducted up and down over a series of idler and/or driven rolls I2. The water-box I I is supplied with circulating, relatively pure, water introduced at a temperature of, for instance, 150

F. through the pipe I3 which is controlled by a suitable valve for regulating the iniiow of water. The tank is provided with a suitable overow I4. From the water-box II, the laminated stock is led through the squeegee device I over rolls I6 into the casing II in which it is conducted over` rolls I8. In this casing I'I, the water is removed from the laminated stock by evaporation, warm air being circulated through the casing I'I as indicated. From the casing I1, the completely dried laminated stock is led over rolls I9 onto the wind-up 20, upon which it is wound in suitable lengths, cut off, and taken to storage.

Numerous other solvent cements may be employed in cementing together the thin sheetings, such for instance as a mixture of acetone and methyl alcohol, ethylene chloride and ethyl alcohol and various other solvents for the particular cellulose sheeting which is being laminated, the solvents necessary for such purpose being Well known to those skilled in the cellulose derivative art. These solvents may also have added thereto a small proportion of the cellulose derivative being cemented, if desired. These are all referred to hereinafter as a solvent cement.

The number of rolls I or curing drums 8 in the chamber 6 may be any desired, it being the purpose of this air-curing treatment to remove as much solvent as can be completely and practically done by air without unduly slowing up the process. The drums 8 may be heated to a tem.- perature anywhere from 150 to 250 F. depending upon the speed with which the nlm is traveling, it being undesirable, of course, to employ a temperature so high as will cause any decomposition of the film. The air that is circulated through this casing 6 may be introduced, say at a temperature of 150 F., although higher or lower temperatures may be employed.

'Ihe speed with which the water is circulated through the water-box I I depends, of course, upon the amount of solvent to be removed from the sheeting, the temperature at which the water is introduced and the length of time the sheeting remains in the water-box. It is best to lean upon the side of having an excess supply of water circulating through the water-box, the exact amount being determined by testing samples of laminated stock which have been subjected to this treatment to ascertain whether the solventhas been suiiiciently removed for the purpose desired. As above stated, the water may be introduced at 150 F. or higher, although too high a water temperature has, with certain solvents such as acetone in the sheeting, been found to give blushing in the sheeting.

The number of rolls provided in the casing I'I is optional, the sheeting being maintained in the casing I'I merely for suflicient length of time to completely remove all water and moisture from the sheeting.

Laminated stock produced as above described will be found to possess only a fraction of a percent, such as .1 or .2 of a percent, of shrinkage even after being tested by soaking in water for 24 hours and then drying. Photographic film produced by coating photographic emulsions upon such laminated stock is eminently suited as a non-shrinking lm for purposes of making maps, and the like, by aerial photography. Numerous variations in the apparatus and process above described will occur, of course, to those skilled in the art, such as variations in size of curing casings, the number of rolls they will employ, the temperature of curing and the like. However, all of these variations come under the teachings of my invention and, it will be understood, are to be included in theclaims appended hereto.

What I claim as my invention and desire to be secured by Letters Patent of the United States 1. The process which comprises laminating, by the use of a solvent cement, a plurality of cellulosev derivative sheets and treating such laminated stock with water to remove residual solvent therefrom.

2. The process which comprises laminating, by the use of a solvent cement, a plurality of cellulose derivative sheets and treating such laminated stock with water at an elevated temperature to remove residual solvent therefrom.

3. 'Ihe process which comprises laminating by the use of a solvent cement a plurality of cellulose derivative sheets and treating such laminated stock with water at a temperature ranging from approximately 150 F. to 200 F.

4. The process which comprises laminating, by the use of a solvent cement, a plurality of cellulose derivative sheets and treating such laminated stock with water at a temperature ranging from approximately 150 F. to 200 F.

5. Ihe process which comprises laminating by the use of a solvent cement a plurality of cellulose derivative sheets, treating such laminated stock with water to remove residual solvent therefrom and drying the laminated stock to remove the water therefrom.

6. The process which comprises laminating, by the use of solvent cement, a plurality of cellulose acetate sheets and treating such laminated stock with water at an elevated temperature to remove residual solvent therefrom.

'7. The process which comprises laminating, by the use of solvent cement, a plurality of cellulose nitrate sheets and treating such laminated stock with water at an elevated temperature to remove residual solvent therefrom.

8. The process which comprises laminating, by the use of an acetone cement, a plurality of cellulose derivative sheets and treating such laminated stock with water at an elevated temperature to remove residual solvent therefrom.

9. The process which compriseslaminating, by the use of an acetone cement, a plurality of cellulose acetate sheets and treating such laminated stock with water at an elevated temperature to 5 remove residual solvent therefrom.

10. The process which comprises laminating,

by the use of an acetone cement, a plurality of cellulose nitrate sheets and treating such laminated stock with Water at an elevated temperature to remove residual solvent therefrom.

HENRY E. VAN DERHOEF. 

